Electric circuit breaker



Filed NOV. 9. 1937 6 Sheets-Sheet 1 March 25, 1941.

D. RCNNBERG 2,235,901

ELECTRIC CIRCUIT BREAKER Filed Nov. 9, 1937 6 Sheets-Sheet 2 asheets-sheet s 1 C o 1L Q 0 N 5% 1% l w 4E m D. RONNBERG ELECTRICCIRCUIT BREAKER Filed Nov. e. 1937 March 25, 1941.

March 25, 1941.

D. RONNBERG 2,235,901

ELECTRIC CIRCUIT BREAKER Filed Nov. 9,1937 6 Sheets-Sheet 4' Fig (9 6Sheets-Sheet 5 fm e/zfar pe/rauma fW/orney.

@011 (P5 Fo'hnr D RUNNBERG ELECTRIC CIRCUIT BREAKER FllBd Nov 9. 1937March 25, 1941.

Patented Mar. 25, 1941 ELECTRIC CIRCUIT BREAKER Daniel Riinnberg,Ludvika, Sweden, assignor to Allmanna Svenska Elektriska Aktiebolaget,Vasteras, Sweden, a corporation of Sweden Application November 9, 1937,Serial No. 173,585 In Sweden November 14, 1936 6 Claims. (Cl. 200-450)In electric circuit breakers, the arrangement pairs, one of which themain pair has been arof extinguishing pots surrounding the breakingranged inside an extinguishing pot and intended gap, in which the arc isbrought in intimate confor breaking the circuit, whereas the othercontact with a flow of an extinguishing liquid or gas, tact pair theauxiliary pair intended for the closhas considerably increased thebreaking ability ing of the circuit has been arranged outside the of thecircuit breakers. In spite of the fact that extinguishing pot, but [incontradiction to the the provision of extinguishing pots of the aboveknown circuit breakers, where the two contact mentioned kind hasconsiderably increased the pairs have been independently actuated by thebreaking ability, however, no corresponding inoperating mechanism]according to the present 10 crease of the ability of the circuit breakerto close invention, one of the contact pairs is directly 10 a currenthas been obtained, at least if the voltoperated by the operatingmechanism and the age has been high. This is due to the fact that othercontact pair is operated by one of the conwhen closing a circuit, atleast when the voltage tacts in the first-mentioned contact pair. ishigh, an arc is lighted in the extinguishing pot, By the abovearrangement of the contacts oi and this causes a sudden shock ofpressure, which the two contact pairs a very convenient and suit- 15 ifthe current is high can be so powerful that the able form of circuitbreaker is attained, especially extinguishing pot will burst. withrespect to the insulation, so that without The pressure generated by anarc increases any difiiculties it can be adapted for high tenwith theamount of heat generated by the arc, sions. This is due to the fact thatonly one of and the amount of heat generated per unit of the contactpairs is directly connected with the 20 time is directly proportional tothe product of operating mechanism. Further the auxiliary conthe arcvoltage and the current. The are voltage tact pair intended for theclosing of the circuit in turn is proportional to the length of the arcmay also be so arranged that it serves for interand to the existingpressure. It is therefore clear ruption of the circuit in cooperationwith the that the pressure arising in the first moment of C a P in theeXtinguiShing D closing of the circuit must be higher than the On theaccompanying drawing several forms of pressure arising at interruptionof the circuit, the invention are shown. Fig. 1 shows schematibecausewhen the arc is lighted at closing the cally one pole of a circuitbreaker with one of circuit, the contacts are at a rather great disthecontacts of the main contact pair movable 3o tance from each otherwhereas at the interruptand connected with one of the contacts of theing of the circuit, the arc is formed between the auxiliary contact pairwhich is arranged outside contacts when they are in immediate proximityof the extinguishing pot but inside a container of each other. If thebreaking point is enclosed enclosing the extinguishing pot. in anextinguishing pot, the arc voltage and Fig. 2 shows the auxiliarycontact pair arthus the pressure is further increased by the rangedbelow the extinguishing pot with one of 35 resistance against anequalization of the pres its contacts connected with the operatingmechsure depending upon the fact that the arc is anism, and its othercontacts connected with the enclosed in a comparatively confined space.movable contact of the main contact pair, the

In order to increase the ability of a circuit contact connected with theoperating mechanism breaker to close a circuit when the current is beingprovided with a piston which by the aid 4 large, it has previously beenproposed to provide of a liquid column actuates the main contact thecircuit breaker with two series connected pair so that it is closedbefore the auxiliary concontact pairs, one of which has been enclosed intact pair is closed. an extinguishing pot and chiefly intended for theFig. 3 shows a slight modification of the aropening of the circuit,whereas the other, which rangement of Fig. 2. 45 had for its purposeonly to close the circuit, has Fig. 4 shows an extinguishing pot inwhich been arranged outside the extinguishing pot. Inone of the contactsof the auxiliary contact pair stead of the provision of an auxiliarycontact is connected with a differential piston actuated pair outsideit, it has also been proposed to proby the pressure generated by thearc, this, piston vide the extinguishing chamber with special memhavingthe function to open the auxiliary contact 50 bers, by which theextinguishing pot has been pair. In this form also an insulating wall isopened when closing the circuit but closed when provided which has anopening traversed by one interrupting the circuit. of the contacts ofthe auxiliary contact pair so The present invention also refers tocircuit that when opening the circuit breaker this conbreakers of thekind provided with two contact tact is washed by a flow of fluid.

Fig. 5 shows the same arrangement as Fig. 4 but with an additionaldifierential piston which causes a flow of fluid against the arc betweenthe contacts of the main contact pair.

Fig. 6 shows the same arrangement as Fig. 4 but with an additionaldifierential piston which causes a flow of fluid through the walltraversed by one of the contacts of the auxiliary contact pair.

Fig. 7 shows a combination of the arrange ments shown in Figs. 5 and 6and is thus provided with two additional differential pistons.

Fig. 8 shows in detail a vertical section of the arrangement shownschematically in Fig. 5, and

Fig. 9 is a detail section of the arrangement shown in Fig. '7.

Fig. 10 is a detail section of a modified form of the arrangementschematically illustrated in Fig. 5.

In Fig. l, I designates a. container filled with an insulating medium.This container contains the two contact pairs and the bottom of thecontainer is provided with an opening for the corn tact 2 operated bythe operating mechanism of the breaker. This contact extends in theclosed position of the circuit breaker into the extinguishing pot 3,which consists of an upper cylinder 3 and a lower cylinder 5, whichlatter has a smaller diameter than the former. The extinguishing pot isclosed at its lower extremity by a bottom 6 and at the top by a cover 7.In the double cylinder thus formed there is provided a differentialpiston 8, which at the top has a collar 9, which fits the cylinder 4 andat the bottom has a collar I II, which fits the cylinder 5. The bottomII of the differential piston is of insulating material and is providedwith an opening I2 for the movable contact 2. The stationary contact I3is attached to a rod I4, which on the other end. carries a contact I5.This rod extends through an opening I6 in the cover I. Immedi atelyabove the stationary contact I3 is a piston I? attached to the rod I4.The rod I4 is surrounded by a cylinder I8, which at the top has a coverIS] with an opening 20 for the rod I l. This cylinder has on the outerside a collar 2I, which can be pressed tightly against the cover 1. The

stationary contact I3 is normally held in its lower position by means ofa helical spring 22, which at the lower end rests on the piston I1 andat the upper end against the cover I9 of the cylinder I8. This helicalspring presses the cylinder I S upwards so that the collar 2I ispressedagainst the cover I. The cylinder I8 is provided with openings 23, thepurpose of which is described below. The piston II has such a diameterthat it tightly slides inside the cylinder I8. The extinguishing pot 3is supported by the leading-in conductor as by means of a disc 25 andinsulating rods or an insulating cylinder 26. In the case that it is acylinder, this is provided with openings on the side. On the disc 25 acontact 21 is fastened, with which the contact I5 can be brought intoengagement.

The arrangement acts in the following way. When closing the circuitbreaker, the main contact 2 is moved upwards and is brought intoengagement with the contact I3, which by a further movement of thecontact 2 i moved upwards until the contact I5 auxiliary is caused toengage with the contact 27. When the contact I3 moves upwards, the fluidin the cylinder I8 is partly forced out through the openings 23 andthence through the space between the collar 2| and the cover '1 into thespace 3I. When opening the the outer container I.

circuit breaker, the contact I3 is held back by the piston II. When thepiston I'I tends to move downwards, a vacuum is created on the upperside of it, so that the cylinder I8 is raised a little, and the collar2i is tightly pressed against the cover 7. The opening of the circuitwill therefore take place between the contacts 2 and I3 and theextinguishing pot will then act in the common manner, so that thepressure developed in it acts on the piston 8 which moves downwardsthereby forcing the extinguishing medium from the space 32 through theopening I2 into the space 35, and at the same time extinguishing mediumis forced out from the annular shaped space 33, which is in freecommunication with v The openings in the cylinder 'l are so dimensionedthat extinguishing medium'may stream out through them, but they are sorestricted that at the breaking a suiiicient pressure can arise in thepot for moving the piston 8. The downward motion of the contact I3 iseffected by the action of the spring 22. This downward motion is,however, so delayed that a vacuum is formed above the piston I'I due tothe fact that, by the pressure in the pot, the collar 25 is pressed upagainst the cover I. The tightening between this collar 2I and the coverI is not complete, however, and the time for the motion of the piston IIwill therefore depend upon the leakage between the collar 2I and thecover 5,

I and by the choice of a suitable leakage the separation of the contactsI5 and 2'! can be so delayed that the interruption of the circuit willalways be completed by the contacts 2 and I3.

The container I is closed by a cover 34!, which i is provided with largeopenings for the escape of the gases. Instead of attaching the contact I3 on the rod I i, it is also possible to have it formed as a sleevecontact and attached to the cylinder 8. The movable contact 2 will inthis case pass through the contact I3 up against the piston I! thusmoving it and the rod I4 until the contact 55 engages with the contact21.

In the form shown in Fig. 2, 37 designates a cylinder with a cover 36.The stationary contact is fastened to thi cover. The cylinder 3'1 isprovided with an inwardly bent edge 59, on which an insulating cylinder38 is fastened. This cylinder 38 has an intermediary wall 39, which isprovided with an opening for a contact 42.

This contact is connected to a piston 43 movable in the cylinder 38,which piston also carries a contact i l, with which the contact 45connected to the operating mechanism of the circuit can be caused toengage. The contact 45 carries a piston 45, which fits the cylinder 38.In the extinguish- 111g pot formed by the cylinders 31 and 38 there is adifferential piston 48 with bottom 49. This piston is normally held inits upper position by means of a helical spring 59. The cylinder 37 isprovided on its side with openings 5| and in the same manner thecylinder 38 is provided with openings The contacts 52 and 44 with pistonare normally pressed against the ring H by means of a helical spring 4?.

This arrangement acts in the following Way. When closing the circuitbreaker, the piston 46 enters the cylinder 38, and as it moves upwardsthe fluid in the space 52 is moved upwards and moves the piston &3 sothat the contact 42 is caused to engage the contact 35, At first afterthe contact =32 engages the contact 35 the piston 43 reaches theopenings 40. The fluid pressed by the piston 66 will therefore, after ithas served for the displacement of the contact 42, flow out through theopenings 40 and the contact 45 is on further upward motion caused toengage the contact 44. No pressure is thus developed in theextinguishing pot, and if an arc should ignite between the contacts 44and 45, the gases generated thereby will escape through the openings 40.At the opening of the circuit breaker in the common manner, a pressurewill arise in the extinguishing pot and will move the piston 48downwards, The fluid enclosed in the space 56 will then stream throughthe openings 5|, and as long as the contact 42 still occupies theopening in the intermediary wall 39, the fluid in the space 54 will flowout through the opening in the piston bottom 49 into the space 55, andat the further motion of the contact 45, the contact 42 is moveddownwards by the helical spring 41, but when the piston 43 has reachedthe ring 4|, the contact 42 can no longer move downwards. The upper tipof it will therefore remain immediately before the opening in theintermediary wall 39, which is the most advantageous position of thecontact in relation to the opening in the intermediary wall in order toget the most favourable extinguishing conditions. As soon as the openingin the intermediary wall 39 is made free, liquid and gas from theextinguishing pot will be blown out through this opening and through theopenings 48.

The arrangement according to Fig. 3 differs from the arrangement shownin Fig. 2 chiefly in that the differential piston is arranged around theextinguishing pot instead of inside it. The differential piston is inthis case formed by the cover 36, which is provided with an opening forthe rod 65, and by the cylinder 31, which is provided with an inwardlydirected collar 59, which tightly fits the cylinder 63. This cylinderand the cylinder 60 with its collar are carried by the rod 65.

The arrangement acts in the same manner as the arrangement shown in thepreceding figure, so that the piston 46 forces the fluid in the space 52upwards, which fluid then actuates the piston 43 until the contact 42engages the stationary contact 35. With this motion, the contact 42moves through the opening 62 in the insulating intermediary wall 6|.When the piston 43 has moved a sufiiciently long way, the space 52 isbrought into communication with the space out side the cylinder 38 bythe openings 40, so that the gases, which may be developed by an arebetween the contacts 44 and 45 easily can escape. The pressure generatedat the breaking is transmitted from the space 55 to the space 55, butalso through the opening 62 to the spaces 54 and 51. The pressuregenerated by the arc moves the piston 36, 31 against the action of thehelical spring 50; so that the space 51 is decreased, and the fluid inthis space will therefore be forced through the openings 58 into thespace 54 and from there through the channels 62 into the space 55. As inthe preceding figure, the motion of the contact 42 is limited by thering 4|, so that also in this arrangement the tip of the contact 42 willstop in the position most suitable for the extinction. The arrangementmay be such that the contact 42 in its end position rests in the openingin the bottom 64, but it is also possible to provide a form, where itmoves so far that the opening in the intermediary wall 64 is free sothat gas and liquid can escape through this opening.

In Fig. 4, 1| designates a cylinder of insulating material, which at thelower end is provided with a bottom 12 also of insulating material, Thisis provided with an opening 13 for the movable contact 14. The othercontact of the contact pair in the extinguishing pot is designated by15, and this contact is by means of the cylinder 16 connected with thepiston 11, which is movable in the cylinder 18. The piston 11 isactuated by a helical spring 8| and the space between the cylinders 16and 18 communicates by means of a channel 89 with the space outside theextinguishing pot. The extinguishing pot is at the top closed by anintermediary wall 83 of insulating material, which wall has an opening82 for one of the contacts 19 of the contact pair outside theextinguishing pot. The other contact in this pair of contacts isdesignated by 84, and the space in which the contact pair 19, 84 iscontained communicates by means of large openings 85 with the spaceoutside the extinguishing pot.

This arrangement acts in the following way.

When opening the circuit breaker the contact 14 H is drawn downwards,and then an arc is formed between the contacts 14 and 15. This generatesin the extinguishing pot a pressure, which acts on the upper side of thepiston 11, which moves downwards and pulls the contact 19 out of contactwith the contact 84 and down through the opening 82. As soon as thisopening has been liberated, a flow of extinguishing medium in contactwith the arc is caused between the contacts 19 and 84. There willtherefore in this form be two series connected arcs, one are between thecontacts 14 and 15 and one arc between the contacts 19 and 84, whicharcs are extinguished by the extinguishing medium flowing through theopenings 13 and 82 respectively.

The arrangement shown in Fig. 5 differs from that of Fig. 4 in that theextinguishing pot is provided with a differential piston 9|, which inthe bottom has an opening 92 for the contact 14. This differentialpiston is normally held in its upper position by a helical spring 94,which at the lower end rests against the inwardly bent part 86 of thecylinder 1|. This inwardly bent part carries also an insulating cylinder81, which thus forms an extension of the extinguishing pot and is closedat the lower end by a bottom 12 of insulating material. In this bottomthere is a hole 99 for the contact 14 and back valves 89. In thecylinder 1| are openings 93 in order to allow the extinguishing mediumbelow the flange of the differential piston to escape from theextinguishing pot.

In the form shown in F g. 6, the cylinder 81 instead of forming anextension downwards forms an extension. upwards of the cylinder 1| andthe differential piston is in this form arranged in the upper part ofthe extinguishing not so that b it a blow-out of the extinguishingmedium through the opening 82 is effected. In the form of the circuitbreaker shown in this figure the same extinguishing action is obtainedbetween the contacts 14 and 15 as in the arrangement according to Fig.4, but at the contacts 19 and 84 a considerably increased extinguishingaction is obtained by means of the powerful stream of extinguishingmedium forced out through the opening 82 by means of the piston 9|.

The arrangement according to Fig. 7 differs from the preceding one onlyin that the extinguishing pot is provided with two differential pistons9|, of which the lower one causes an extinction of the arc between thecontacts 14 and 15 and the upper an extinction of the are between thecontacts 19 and 84.

In Fig. 8 an arrangement principally the same as in Fig. 5 is shown indetail. In this figure, IOI designates the stationary contact in theextinguishing chamber and I02 the movable contact. The stationarycontact is, however, to a certain extent movable and is connected with adifierential piston described below. The extinguishing pot itself isformed by an insulating cylinder I03, which is fastened to a metalcylinder I04, which in turn is fastened to an annular part I05 of metal,and this part is upwardly continued by an insulating cylinder I03,fastened to a cover I61 carrying the extinguishing pot.

In the extinguishing pot there is a differential piston I90 consistingof an insulating cylinder I09 with bottom H0, which is also ofinsulating material and is provided with a flange III. The intermediarypart I05 consists of a ring I I2 and a ring H3, which by means of armsH4 carries a nave II 5. In this nave a metal cylinder II 6 is inserted,and in this cylinder another cylinder II! with a tightening ring H8moves. The cylinder II! also fits in a tightening ring H9 of the nave II5.

The cylinder II'I carries the stationary contact IIII, which in a knownmanner is formed as a sleeve contact, and further the cylinder IITcarries a pipe I20, which at the upper end is closed by one of thecontacts I2I in the auxiliary contact pair outside the extinguishingpot.

In the cylinder I06 there is an intermediary wall I22 with an openingI23, through which the auxiliary contact I2I can pass on its way to itscounter-contact I24. The space in the cylinder m6, which contains thiscontact is connected by large openings I25 with the space outside thecylinder I06, so that the contact pair IZI, I24 can be regarded asarranged outside the extinguishing pot.

Between the nave H5 and the cylinder H6 there is a space I26, which isin communication with the space outside the extinguishing pot throughchannels I 21 in the arms H4. These channels are provided with ballvalves I28, which allow liquid to enter the space I26, but preventliquid escaping from this space. In one or a plurality of the channelsin the arms H4, the ball valves are replaced by plugs which seep holesof suitable size.

The ball valves I28 consist of a cylinder I29, which at the outer end isprovided with an inwardly directed rand I30. Immediately to this randthe cylinder is provided with two or several holes I3I, and in thecylinder there is a ball I32, and the motion of this ball is outwardlylimited by the said rand, and its motion inwardly is limited by a pinI33.

The space below the differential piston I is on the drawings designatedby I34 and the space above it by I35, and further the space above theintermediary wall I22 is designated by I35.

The arrangement acts in the following way. When closing the circuitbreaker, the movable contact I02 is moved up against the stationarycontact IIII and then moves the cylinder III with pipe I20 and contactI2I upwards, so that the latter is caused to engage the contact I2 4.The closing of the circuit will therefore take place between the twolatter contacts, and if then an arc is ignited, the gases generated byit will escape through the openings I 25. During the upward motion ofthe cylinder II'I, liquid is sucked into the space I 26 through the ballvalves I28.

When opening the circuit breaker, the interruption of the circuit takesplace between the contacts IOI and I02. The pressure then generated inthe extinguishing pot acts on the differential piston I08, so that itmoves: downwards. (Normally the piston I08 is held in its upper positionby means of the helical spring I31.)

The pressure in the pot also acts on the upper side of the bottom in thecylinder III. In fact, the cylinder II'I serves as a differential pistonand tends to move downwards partly due to the pressure acting on it andpartly due to the action of the helical spring I38. This downward motionis, however, damped by the liquid in the space I 26, which liquid canescape only through the above mentioned seep holes in some of the armsH4, and by regulating these seep holes the damping of the motion of thecylinder I I I can be regulated.

When the cylinder II'I moves downwards, the contact I2I is also moveddownwards, and when it has passed through the opening I23, here also anextinguishing action is added to the extinguishing action provided inthe opening of the bottom H0.

The damping of the motion of the contact IIII is connected with theadvantage that with small currents the distance between the contact WIand the bottom H0 a longer time is maintained at a large value than ifthe current is large. The larger the current is the higher will be thepressure in the pot and the faster will the cylinder I I1 movedownwards. In this way a smaller arc length is attained when the currentis large, so that the energy developed by the arc during theinterruption will be comparatively independent of the magnitude of thecurrent traversing the circuit breaker when interruption takes place.

The fact that the space covered by the larger surface of thedifferential piston is opened and brought into communication with thespace outside the extinguishing pot when the auxiliary contact movesdownwards is followed by the great advantage that the piston in ashorter time can move back into the original position, because the gasgenerated in the extinguishing pot can easily escape through the openingfor the auxiliary contact as the pressure on both sides of thedifierential piston will then be equal. The helical spring I31 can movethe piston back to the original position without any great resistance.

The arrangement according to Fig. 8 is in some cases followed by thedisadvantage that if an arc is ignited between the contacts I2I and I24before the contact I2I has reached the opening I23, the pressuregenerated in the space I36 can be transmitted through the hole I23 andthus cause a motion of the piston H18.

Fig. 9 shows in detail a form which principally is the same as the formshown in Fig. 7. In this form the above disadvantage is eliminated sinceas in Fig. 7 a difierential piston is arranged in the upper part of theextinguishing pot. This piston will cause a stream of extinguishingmedium through the hole I23 when the contact I2I is drawn away from thishole.

In Fig. 9, IIII designates the stationary contact and I82 the movableone. The extinguishing pot is formed by a cylinder I04, which at thelower end carries a cylinder I03. The cylinder IM is in turn carried byan intermediary part I consisting of a ring H2 and a ring H3. The ringII3 carries by means of arms H4 a nave 7 H5. On the ring II 3 a cylinderI39 is fastened,

which is continued upwardly by a cylinder I40, which is provided with anintermediary wall I22 with an opening I23 for the contact I2I. Thecylinder I40 is at the upper end closed by the cover I01, but the spaceI36 between the intermediary wall I22 and the cover I01 communicates bylarge openings I25 with a space outside the extinguishing pot. In thecylinders I04, I03 there is a differential piston I08, which consists ofa cylinder I09 with bottom I I and flange III. In the cylinders I39 andI40 there is another difierential piston I4I, through which the contactI2I passes. The differential piston 508 is normally held in its upperposition by means of the helical spring I31, and the differential pistonMI is normally held in its lower position by means of the helical springI43. On the nave H a cylinder H6 is fastened. In this cylinder anothercylinder H1 is movable. This carries at the lower end the stationarycontact IEII and is at the upper end provided with a tightening ring H8,which slides in the cylinder H6. The nave H5 has at the lower end aninwardly bent part, which fits the cylinder H1, and further the cylinderH1 is provided with a rim II9, which tightening ring H8 slides in thecylinder H6. The cylinder H8 may have an inner diameter decreasingdownwards, which diameter at the lowermost part of the cylinder H8 isthe same as the outer diameter of the ring IE9. The contact IN is joinedby means of the pipe I20 to the contact I2I. The cylinder H1 withcontact IIII is normally held in its lower position by means of thehelical spring I38. The arms H4 are all, or only some of them, providedwith channels I21, by which the space inside the nave H5 is incommunication with the space outside the extinguishing pot, and furtherthe cylinder H6 is provided with openings I5I, which connect the spacebetween the cylinder H6 and the cylinder II1 with the space inside thenave I I5.

This arrangement acts in the following way. When closing the circuitbreaker, the contacts IOI and I02 are brought into engagement with eachother, and when the contact I02 moves upwards the contact I2I also ismoved upwards through the hole I23, so that it is brought intoengagement with the contact I24. The spring I38 is then pressedtogether.

When opening the circuit breaker, the contact I02 is pulled downwardsand in the first moment the contacts WI and I02 are separated. By meansof the pressure generated by the are formed between these contacts, thedifferential piston I08 is moved downwards and at the same time thedifierential piston MI is moved upwards. The pressure generated by theare between the contacts IOI and I02 acts at the upper side of thecylinder H1 and tends to move this cylinder with the contact IOI and thecontact I2I downwards. This motion is, however, damped by the liquidenclosed in the space below the rim H9 between this rim and the lowerinwardly bent part of the nave I I5. This liquid must in escaping to thespace outside the extinguishing pot pass the rim IIS into the space I20and from there through the openings I5I and the channels I21. Due to thefact that the cylinder H6 inwardly has a downwardly decreasing diameter,the play between the rim I I 9 and the inner wall of the cylinder H6will decrease when the cylinder II1 moves downwards, so that asuccessively increasing damping of the motion of the cylinder H1 isobtained. When the contact I 2I is moved so far downwards that theopening I23 has been liberated, the differential piston I4I forcesextinguishing medium from the space I44 through the opening I23. A partof this extinguishing medium will traverse the bore I42 in the contactI2I and from there out through the openings on the side of the pipe I20.

When closing the circuit breaker, the contacts IOI and I02 at first arebrought into engagement with each other, and firstly after this contactis completed, the contact I2I commences the motion upwards. When an arcis then ignited between the contacts I2I and I24, the gases generated bythis are will escape through the openings I25.

The arrangement according to Fig. differs from that of Fig. 9 in thatthe differential piston MI is replaced by an intermediary wall I45,which is provided with openings I46, the said openings being closed byback valves I41. A pressure generated in the space I44 therefore can notbe transmitted to the space I35 and cause a motion of the piston I08. Onthe contrary, the pressure generated by the are between the contacts IOIand I02 can if it is sufficiently high allow a flow of liquid from thespace I35 out through the openings I46 into the space I44 and from therethrough the opening I23. The gases which are generated by the arcbetween the contacts I2I and I24 can escape partly through the openingsI25 and partly through the bore I48 and the openings I49 on the side ofthe pipe I24 out into the channels I50. In other respects the form shownin Fig. 10 is nearly the same as that shown in Fig. 9.

I claim as my invention:

1. In an electric circuit breaker an arc-extinguishing pot, a maincontact pair enclosed in the said pot, an auxiliary contact pairarranged outside the pot and series connected with the main contactpair, a dash pot mechanism retarding the opening of the auxiliarycontact pair, an operating mechanism acting on the main contact pair, aspring acting on the auxiliary contact pair in the opening direction,and a difierential piston actuated by the pressure generated by the arcin the arc extinguishing pot, said piston being connected with one ofthe contacts in the auxiliary contact pair and acting in the openingdirection.

2. In an electric circuit breaker an arc-extinguishing pot, a maincontact pair enclosed in the said pot, an auxiliary contact pairarranged outside the pot and series connected with the main contactpair, a dash pot mechanism retarding the opening of the auxiliarycontact pair, an operating mechanism acting on the main contact pair, aspring acting on the auxiliary contact pair in the opening direction, adifierential piston actuated by the pressure generated by the arc in thearc extinguishing pot, said piston being connected with one of thecontacts in the auxiliary contact pair and acting in the openingdirection, and an insulating wall of the arc extinguishing pot providedwith an opening traversed by the contact of the auxiliary contact pairconnected with the differential piston.

3. In an electric circuit breaker an arc-extinguishing pot, a maincontact pair enclosed in the said pot, an auxiliary contact pairarranged outside the pot and series connected with the main contactpair, a dash pot mechanism retarding the opening of the auxiliarycontact pair, an operating mechanism acting on the main contact pair, aspring acting on the auxiliary contact pair in the opening direction, adifferential piston actuated by the pressure generated by the arc in thearc extinguishing pot, said piston being connected with one of thecontacts in the auxiliary contact pair and acting in the openingdirection, an insulating wall of the arc extinguishing pot provided withan Opening traversed by the contact of the auxiliary contact pairconnected with the differential piston, and a further difierentialpiston arranged inside the extinguishing pot causin a flow of fluid incontact with the are between the main contacts.

4. In an electric circuit breaker an arc-extinguishing pot, a maincontact pair enclosed in the said pot, an auxiliary contact pairarranged outside the pot and series connected with the main contactpair, means for closing the main contact pair and afterwards theauxiliary contact pair, a differential piston actuated by the pressuregenerated by the arc in the arc extinguishing pot, said piston beingconnected with one of the contacts in the auxiliary contact pair andwith the stationary contact of the main contact pair, an insulating wallof the arc extinguishing pot provided with an opening traversed by thecontact of the auxiliary contact pair, actuated by the differentialpiston, a retarding device for the motion of the differential piston, afurther diiferential piston arranged inside the extinguishing potcausing a flow of fluid in contact with the are between the maincontacts, and a differential piston arranged inside the extinguishingpot, causing a flow of gases and liquid through the opening in theinsulating wall of the pot, traversed by one of the contacts of theauxiliary contact pair.

5. In an electric circuit breaker with are extinguishing pots, a maincontact pair enclosed in each extinguishing pot, an auxiliary contactpair arranged outside the extinguishing pot and series connected withthe main contact pair, means for closing the main contact pair andafterwards the auxiliary contact pair, a diiferential piston actuated bythe pressure generated by the arc in the arc extinguishing pot, saidpiston being connected with one of the contacts in the auxiliary contactpair and the stationary contact of the contact pair inside the arcextinguishing pot, an insulating wall of the arc extinguishing potprovided with an opening traversed by the contact of the auxiliarycontact pair connected with the diiTerential piston, a retarding devicefor the motion of the difierential piston; a further differential pistonarranged inside the extinguishing pot causing a flow of fluid in contactwith the are between the main contacts, and an insulating Wall arrangedinside the said insulating wall of the pot, provided with valvesallowing a flow of gases and liquid only from the extinguishing pot tothe space outside it.

6. In an electric circuit breaker with arc extinguishing pots, a maincontact pair enclosed in each extinguishing pot, an auxiliary contactpair arranged outside the extinguishing pot and series connected withthe main contact pair, means for closing the main contact pair andafterwards the auxiliary contact pair, a differential piston actuated bythe pressure generated by the arc in the arc extinguishing pot, saidpiston being connected with one of the contacts in the auxiliary contactpair and the stationary contact of the main contact pair, an insulatingwall of the arc extinguishing pot provided with an opening traversed bythe contact of the auxiliary contact pair actuated by the differentialpiston, a retarding device for the motion of the difierential piston, afurther clifierential piston arranged inside the extinguishing potcausing a flow of fluid in contact with the arc between the maincontacts, and a difierential piston arranged inside the extinguishingpot, causing a flow of gases and liquid through the opening in theinsulating wall of the pot, traversed by one of the contacts of theauxiliary contact pair.

DANIEL RoNNBERG.

